#!/usr/bin/bash

a="abc"
b="efg"

if [ $a == $b ]
then
	echo "a == b"
else
	echo "a != b"
fi

if [ $a != $b ]
then
	echo "a != b"
else
	echo "a == b"
fi

if [ -z $a ]
then
	echo "a is null"
else 
	echo "a is not null"
fi

if [ -n $a ]
then
	echo "a is not null"
else
	echo "a is null"
fi

if [ $a ]
then
	echo "a is not null"
else
	echo "a is null"
fi

